This invention relates to tube cutting devices and, more particularly, to a method and apparatus for separating flat heat exchanger tubing into predetermined lengths having substantially burr-free parted ends.
Conventional heat exchanger tubing is fabricated from thin-walled copper pipe, which is bent in a serpentine pattern and provided with heat exchanging fins. It has long been recognized that care must taken in cutting the tubing to minimize the formation of radially inwardly projecting burrs which are formed by the cutting tools. Typically, the tubing is cut by orbiting a cutting tool about the circumference of the tubing while moving the cutter inwardly.
Various mechanisms have been proposed to minimize formation of burrs on such tubing. One such device is disclosed in U.S. Pat. No. 3,568,488 to Franks. According to the Franks patent, a tube is tightly gripped and placed under tension and while the tube is tensioned, a cutting tool makes an annular cut in the periphery of the tube which penetrates into the wall of the tube. With the tension applied to the tube, the tensile strength of the tube wall not yet severed is exceeded and the tube breaks. Consequently, the tube material is not cut entirely through, but partially cut and partially pulled apart at the cutting point. Therefore, the inwardly extending burr is minimized by the extruding caused by the pulling apart action. Other examples of tube cutting techniques may be found in U.S. Pat. Nos. 4,235,137; 4,112,294; and 3,692,219.
A recent development in heat exchange tubing involves the provision of extruded flat tubing made from aluminum. The flat tubing has flat, parallel faces and rounded ends to define a flat, narrow interior channel. The interior channel is separated into a plurality of axially extending internal chambers defined by parallel walls extending perpendicularly between the flat walls of the tube. This arrangement provides a large surface area to the liquid flowing through the tube. Since the walls defining the internal chambers are so closely spaced, it is imperative that the severed ends of the tubing be substantially burr-free so that the burrs do not block the passages and do not interfere with an edge-to-edge tube joining operation or other operation involving the connection of the tube to a fluid source.